If you consider individual U.S. states as independent economies, then California would be the 12th largest economy in the world. Based on estimates from the International Monetary Fund, California's economy is larger than that of Australia and South Korea (among other developed, first-world nations).

With an economy of this magnitude, there are opportunities aplenty for banks interested in deposits, loans, and cash management -- and not just the megabanks, either.

In the video below, Motley Fool contributor Jay Jenkins finds two regional banks, Union Bancshares (NASDAQ:UNB), U.S. Bancorp (NYSE:USB), and a regional subsidiary of BNP Paribas (OTC:BNPQ.Y), Bank of the West, that are competing on market share against their "too big to fail" megabank competitors.